Layer 3 （the network layer） provides connectivity and path selection between two host systems that may be located on geographically separated networks. Which two devices operate at the network layer？（）

A. assists in locating appropriate resources
B. provides training on products， tools， and solutions
C. provides a direct support path for any partner issue
D. provides validated commercial solutions
E. provides a step-by-step outline of implementation tasks required

A. site-to-site VPN for remote offices
B. business-grade firewall
C. Cisco IOS software-based
D. email security
E. XML support
F. premium support via SMARTnet

A. four station ports and four trunk ports （4xFXS and 4xFXO）
B. two station ports （2xFXS）
C. eight station ports （8xFXS）
D. one station port and one trunk port （1xFXS and 1xFXO）